Electrical precipitator



Oct. 21, 1952 w, SULTIZER 2,614,652

ELECTRICAL. PREC IP ITATOR Filed Aug. 15, 1951 3 Sheets-Sheet l RECOVERYFURNACE WEAK BLACK LIQUOR |3 STORAGE DISSOLVING TANK HEAVY BLACK LIQUORi STD RAGE NORMAN W. SULTZER INVENTOR B 3 9- Erma ATTORNEYS Oct. 21,1952 N. w. SULTZER ELECTRICAL PRECIPITATOR 3 Sheets-Sheet 2 Filed Aug.15, 1951 INVENTOR' LEM NORMAN W. SULTZER ATTORNEYS Oct. 21, 1952 N, w,SULTZER 2,614,652

ELECTRICAL PRECIPITA'VIOR Filed Aug. 15, 1951 3 Sheets-Sheet 3 IN VENTORNORMAN W. SU LTZER BY M ATTORNEY S Patented Oct. 21, 1952 4;;

to ResearchCoi-poration, NewYoi-k, N. Y a corporation of New YorkApplication Au usv s, 1951'," Serial No. 241.53

8 Claims.

This invention relates to tors and more particularly to electricalprecipitators having a liquid-washed devicein the lower portion thereoffor recovering in liquid solution or liquid suspension the precipitatedmaterial.

removed from the precipitator electrodes. More especially, theprecipitator of this invention is adapted to recover sulfatefly-ashinthe" form of an aqueous 'solution'from' the exhaust gases of arecovery furnace burning black liquor from the digesters in a sulfatepaper mill." I I An object of the invention is to provide an electricalprecipitator having an improved device for recovering precipitate inliquid form. *==Another object is to provide in such a precipitator aliquid washed recovery device having no moving parts. 7

Another object is to provide an electrical precipitator of theforegoingtype that is simple to build and operate and that requires aminimum of maintenance care.

Another object is to provide in such a precipitator an arrangement forreducing the foam that tends to be produced with certain 'washingliquids such as black liquor. U

These and other objects of the invention are realized in an electricalprecipitator having a casing, complementary extended surface and hightension electrodes mounted in'a casing, a panel mounted in an inclinedposition in the casing and positioned to receive dust falling from theelectrodesythe panel having a plurality of riffles projecting upwardlytherefrom, means for applying liquid to an elevated "area of the panel,

and sump means below the panelfor' receiving liquid from the n Theinvention will' be described in greater --detail with'reference tothedrawingsin' which? Fig. l is a diagrammatic viewofa' black liquorrecovery systememplo'yint a prec'ipitatorin accordance with theinvention; 3?

Fig; 2 is anend elevational view'of' an" electrical precipitator as usedin the system-of Fig. 1, parts being broken away; Fig. 3 is a sectionalview 3-3- of Fig. 2;-and

Figs. 4 and-5 show details of construction of taken on the line weirpieces at 'the loweredge 'of the flow panels. --Referring to thedrawings, particularly tol' ig. -l-=thereof, the black liquor recoverysystem shown includes a storage tankfor weak black-liquor'receivedthrough the conduit H from the digesters and pulp filters (notshown) of a su l fate paper mill. The weak black liquor is passedthrough a pipe -l2un'der control of valve ';l:3 to

electrical iprecipitaat'which the heavy Ihe-heavy black liquor isconducted by a pipe 15' to a-heavy'black liquor storage tank 16.

a conventional multiple efiect evaporator l4 having-the usual barometriccondenser l5. In the evaporator I4, the black liquor is concentrated byevaporation of water therefrom to a degree black liquor can be burned.

Heavy black liquor from the storage tank it flows through a pipe I! to acharging tank l8 and from thence through the line I!) to a furnacecharging device that introduces a spray of heavy black'liquo'r into therecovery furnace 2|.

Inthe furnace, the heavy black liquor is burned.

' The lignin contained therein, together with other combustiblematerial, oxidized to provide heat that vaporizes the water of theliquor. The furnace action reduces the principal inorganic ingredient/ofthe liquor, sodium sulfate, to sodium sulfide tha't is' the principalcomponent of the furnace ash 22 thatis discharged into a dissolving-tank23. In the dissolving tank, the 'ash is dissolved in water to provide asolution that is subsequently; purified" and reused for digestingadditional quantitiesof wood chips.

Hot gases from the furnace, containing water vapor and products ofcombustion of black liquor. also contain a small but significant burdenof fly ash in susp'ension.- This fly ash contains a large percentage ofsodium sulfate which it is desired to recover from the gases before theyare discharged into theatmosphere.

The hot gases are passed from the furnace througha disc evaporator 24 inwhich some of 29 to be described in greater'detail hereinafter. 'In theprecipitator, the gases are substantially relieved of their burden ofsulfate ash and the cleaned gases pass by way of a flue 30 to a stack(not shown) for discharge to the atmosphere.

- Fly ash precipitated in the electrical precipitator is dissolvedtherein black liquor and the solution is ultimately fed to the blackliquor storage tank l6 through the pipe 3| under control of the valve32. The black liquor used for dissolving the sulfate ash may consist of(1) heavyb1ack..1iquor pumped from the storage nated 29, is shown indetail in Figs. 2 and 3. Referring to these figures, the precipitatorshown has a shell or casing 36 that may be of concrete construction. Gasinlet andsoutletfiuetsfl and 38 are provided and gas flows through thepre cipitator in the direction of the arrows of Fig. 3.

As is usual in such precipitators, a plurality of complementary extendedsurface electrodes 39 and high tension electrodes 40 are positioned inthe casing. The extended surface electrodes Bdmay take the formjofaplurality :Of' vertically disposed, horizontally-spaced. parallel.plates providing. :parallelgducts. 4 I through which-flows the gas to:be. cleaned. The high tension electrodes. 40 are.- discharge electrodesin the form of ,fi'n wires suspende curtai formatio in the gasductsbetween adjeoentplates. Each e.wire as has a tensionin wei ht at thebott that keeps the wire t ut.

Those persons skilledin the a t wi l eadily understand that, in operatn. as to e c eaned is pass d thr u h her eein atorrand h h el cpotential i applied c oss the m:-

elementa y di ch r e and. extended: surfac Co a d s harseoeeu s at e thWire l r de a rtielessu ende i th electrodes.

s s re c ge -,and att c ed hr; he nte e eo ode fie r the. xtended surace ele trodes. The particles are deposited upon the end ur ac e eetr sii' y ibrati er vrapping the electrodes, or otherwise suitablycleaningthem in the'conventional way the precipitate is dislodged fromthe -e lec trodes and allowed to fall into the section of the-precipita--tor beneath the electrodes.

. In accordance with theinvention there-is provided in the casing 36beneath theelectrodes and ina position to receive. dust fallingthereirom a device-for dissolving or suspending the .dust in a liquidmedium. Thisdeviceinoludes a zig-zag arrangement of riiiie-bqards overwhich flows the solvent liquid. and onto at least some 5 of which fallsdust from the precipitator electrodes. This arrangement efiects rapiddissolution .of the dustlin the solvent and the dust is -rernoved fromthe precipitator in the solvent liquid Asseen in Fig. 2 the riille boardstructure-is symmetrical. about ;a vertical plane running through thecenter of the .precipitator; therefore, only one half of the structurewill be dei i The uppermost rifile board includes an inclinedpanel 43that slopes downwardly irqm near-thecenter lineof the precipitatortowards n f the walls hereot: e an le oislone is not critical andmay'range from about to about 35 -Theane s o id d ith a plurality ofupstanding riffles 0r cleats 44 that are arrangedin-spaced parrallelrelation down the slope of the panel 'tointerrupt the smooth flow of;liquid down the panel and cause turbulence in theliquid.

Solvent, liquid-is ted to thedupper area of -'panel :43 from anovenficzw trough :45 that "ex- .member '41 'tion of thebolt holes 50,the weir piece 48 may 41 "and a weir piece 4'8 attached thereto. De-

tails of this construction are best seen in Figs. 4 and 5 wherein it isseen that the weir piece -48 is fastened to the member 41 by means ofbolts 49 passing through vertically elongated ""bolt holesifl in theweir piece and through cir- "cular "close 'fitting bolt holes 5| in thelateral Owing to the elongated configurabe leveled and thereafter boltedsecurely to the member 41.

seen in Figs. 4 and 5, the lower edge 52 of the weir piece depends belowthe bottom of the an 3 and is serrat d t r u out. its le s h- Th s serraed c nst u ti n pr i es a plurality of drip points along the lower edgeo t e we ie and ass u i rm owv o liquid from the weir piece to theimmediately sebi ent fle o d Riiiie board 53 slopes from the outer wallof the c si g 36 b a h. the t m board 3 inward y o e -oi iee n t e c tein oi h precipitator. .Riffle board 53 is similar in construction to theboard 43 described hereinbe- -fore It is provided with cleats 44' and adam at its lower edge including the weir piece 48.

Positioned below the .riflie board 53 is another and similar riiiieboard 54 that slopes from the center towards the outer wall of theprecipitator. The discharge dam including the weirpiece 48]" dischargessolution or liquid to a sump. 55. hav- ,ing a lateral trough 56receiving the solution.

solution is discharged from the trough through the pipe 3|.

Solvent liquid is introduced into the trough 45 thrQliQhlthe inlet pipe33 having a header 5! extending above and parallel to the-trough, theheader being equipped with a plurality of horizontally spaced outletnipples 5t that distribute the liquid into the trough. Additionalliquid, either solvent or plain water, maybe introduced behind. theriiiie board dischar dams through headers 59, 6D and BI havingdistribution nipples '62,

Inbperationin the recovery system of "Fig. 1,

gases from the recovery furnace are 'blbwn throug'h the precipitat'or 29that is energizedin the usual manner. Sulfate ash-is precipitated uponthe collecting electrodes. Black liquor of the desired concentration;isied to the ash dissolving-device through the pipe 33 and additionalblack liquor or water is fed through-headers '59,

60 and GI as may be desirable to increaseliquid flow through thedissolver. Black-liquor flows in a zig-zag path over the riflle-boards43, 53 and 4 nd nto esumpii, ts n w down th rifile boards, the liquor--is continually agitated and any sediment that tends to collect behindthe dams is agitated into suspension byiliquiid rodueedhr ue he n les62- Sulfate ash from-the e ectrodes 39 and Hogans into the black :liquorflowing down the. rifiiezboard 43 and is carried along by the liquoranddissolved therein as the stream flows through the dissolving device.Solution is di$charged through the pipe 'h n8'--. 11..cl0se proximity"to the uppermost, mime 5 boards. A strong electric field is set upbetween the highly charged weights and the grounded uppermost riffieboards and this field tends to break any foam that may form in the blackliquor on the uppermost riffie boards and in the feed trough 45. Also,the concentration of the black liquor is maintained near the point atwhich it has a minimum foaming tendency.

From the foregoing description it is seen that the present inventionprovides an electrical precipitator that accomplishes in a simple waythe Q objects of the invention.

I claim:

1. An electrical precipitator comprising a casing, complementaryextended surface and high tension electrodes mounted in said casing, apanel mounted in an inclined position in said casing and positioned toreceive dust falling from said electrodes, said panel having a pluralityof rifiles projecting upwardly therefrom, means for applying liquid toan elevated area of said panel and sump means below said panel forreceiving liquid from said panel.

2. An electrical precipitator comprising a casing, complementaryextended surface and high tension electrodes mounted in said casing, apanel mounted in an inclined position in said casing and positioned toreceive dust falling from said electrodes, said panel having a pluralityof rifiies projecting upwardly therefrom, means including an overflowtrough positioned adjacent the top of said panel for applying liquid toan elevated area of saidpanel, and sump means below said panel forreceiving liquid from said panel.

overflow dam positioned adjacent the bottom of said panel, and sumpmeans below said panel for receiving liquid from said panel.

4. An electrical precipitator comprising a cas ing, complementaryextended surface and high tension electrodes mounted in said casing, apanel mounted in an inclined position in said casing and positioned toreceive dust falling from said electrodes,-said panel having a pluralityof rifiles projecting upwardly therefrom, means for applying liquid toan elevated area of said panel, an overflow dam positioned adjacent thebottom of said panel, means for introducing additional liquid behind andadjacent said overflow dam, and sump means below said panel forreceiving liquid from said panel.

5. An electrical precipitator comprising a casing, complementaryextended surface and high tension electrodes mounted in said casing, aplurality of inclined panels mounted in zig-zag arrangement in saidcasing, thetopmost of said panels being positioned to receive dustfalling from said electrodes, said panels having rifiles projectingupwardly therefrom, means for applying liquid to an elevated area of thetopmost of said panels, means directing liquid from a lower area of eachsaid panel to an upper area of the immediately subjacent panel, and sumpmeans below the lowermost of said panels receiving liquid from thelatter.

6. An electrical precipitator comprising a casing, complementaryextended surface andhigh tension electrodes mounted in said casing, aplurality of inclined panels mounted in zig-zag arrangement in saidcasing, the topmost of said panels being positioned to receive dustfalling from said electrodes, said panels having riilies projectingupwardly therefrom, means for applying liquid to an elevated area of thetopmost of said panels, means including an overflow dam directing liquidfrom a lower area of each said panel to an upper area of the immediatelysubjacent panel, and sump means below the lowermost of said panelsreceiving liquid from the latter.

'7. An electrical precipitator comprising a casing, complementaryextended surface and high tension electrodes mounted in said casing, aplurality of inclined panels mounted in zig-zag arrangement in saidcasing, the topmost of said panelsbeing positioned to receive dustfalling from said electrodes, said panels having riflles projectingupwardly therefrom, means for applying liquid to an elevated area of thetopmost of said panels, means including an overflow dam having aserrated lower drip edge directing liquid from a lower area of each saidpanel to an upper area of the immediately subjacent panel, and sumpmeans below the lowermost of said panels receiving liquid from thelatter.

8. An electrical precipitator as defined in claim 7 wherein the meansfor applying liquid to the topmost of said panels includes an overflow)trough positioned adjacent the top of said panel.

NORMAN W. SULTZER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 768,450 Hardie Aug. 23, 19041,342,651 Squires June'8, 1920

